Conventional radio telephone systems such as cellular systems use cell-sites having co-located transmitters and receivers to cover small geographical regions referred to as cells. Several cell-sites disposed within a particular geographic area are coupled to a master controller called a mobile telephone switching office (MTSO). The MTSO controls the cell-sites and provides an interface connection to the public switched telephone network (PSTN).
Each conventional cell-site uses pre-assigned channel sets to communicate with mobile units in a service area covered by the cell-site. Each channel set typically includes a pair of carrier frequencies with each carrier frequency being used for respective up-link or down-link communications with a mobile unit. Neighboring cell-sites use different channel sets to avoid interference on the same channel between adjacent service areas.
Conventional cellular systems provide mobility to a subscriber through a procedure referred to as hand-off. According to this procedure, cell-sites which are geographically adjacent are considered to be neighbor cell-sites. A neighbor cell-site is the cell-site to which a call can be transferred to as a mobile unit traverses a current cellsite boundary. The transferring of a call from one cell-site to another is referred to as a hand-off. The parameters which specify the cell-sites that can receive a hand-off from a particular cell-site are included in a table called a neighbor list for that particular cell-site.
The channel sets and neighbor lists assigned to particular cell-sites as well as other system organization parameters, such as the number and transmission power of cell-sites, are typically determined using propagation models prior to installation of a system. After installation with the parameter settings determined by the modeling process, the system coverage area is verified by field testing. During a typical field test, a mobile test unit is moved throughout the service area while the base stations transmit respective test frequencies. As the test unit is moved from one sampling location to the next, the signal strength of the test frequencies and the corresponding geographic location is collected and processed to verify that the system can provide service to the intended coverage area. In some conventional systems, uplink signal strength is also measured from the sampling locations to verify the service area coverage.
If a change in a parameter setting is indicated, then the modeling, implementation and subsequent field testing are performed with the new parameter setting. As a result, conventional installations require a labor intensive, time consuming and costly iterative process of modeling, implementation and verification. Typically, conventional systems do not automatically determine organization parameters. Such automatic determination of parameters is known as "self-organization" in the art.
Other radio telephone systems such as personal communication networks (PCN) and/or indoor cellular systems similarly use localized base stations having smaller service areas than cell-sites. However, the installation of such systems is substantially similar to that previously described for the cellular system and typically requires the labor intensive, time consuming and costly iterative process of modeling, implementation and verification.
To increase the simultaneous communication capacity of a system, channel reuse is employed where two sufficiently distant base stations simultaneously use the same channel. In such systems, estimates of co-channel interference are often used during the modeling stage to insure acceptable quality of the communication link. However, these estimates are typically conservative which limits the communication capacity.
More recently, a limited form of self-organization called dynamic channel allocation has provided greater spectral efficiency and capacity. This technique typically detects interference levels on a set of channels immediately prior to establishing communication with a mobile unit and then establishes such communication using channels in the set with the lowest interference level.
Nevertheless, a need exists for a radio telephone system having enhanced spectral efficiency that uses substantially automated planning, organization and verification during installation that does not require extensive modeling or testing.